People have always been fascinated by fire. Its light and energy provide very useful benefits, and its movement and appearance have pleased countless gazers in a variety of settings, from campgrounds to living rooms. The natural movement of fire provides an almost-lifelike appearance, which contributes substantially to its beauty.
Amplifying the movement of flames can generate an even more pleasing look for observers. One such manner of amplification is to swirl the flame. Swirled flames can have an almost helical look.
Present designs of ‘swirling flame’ gas fireplaces (or similar such aesthetic and/or useful features) rely largely on imparting kinetic energy to a gas in order to cause the flame to move in rotary motion. For example, some approaches use an electric fan to rotate air and any flame that is generated. See, e.g., U.S. Pat. No. 7,175,424. Of course, any mechanical or electrical breakdown would cause the flame to stop rotating and would therefore result in the complete loss of any visual, rotary effect.
Another conventional approach is to provide fireplace or torch with a flame situated within a clear, vertical chimney that admits air in a manner to cause the flame to swirl. In other words, the chimney function is merged with that of a plenum or burn chamber. A burner is positioned at the foot of the chimney. To create a moment about the vertical axis within the chimney, such a chimney is commonly square or rectangular with vertical air slots. Typically, the vertical air slot may be positioned consistently along the same vertical (e.g., leading) edge of each of the faces of the chimney. These vertical air slots admit air into the chimney for combustion. When the flame is started, combustion gasses begin to rise within the chimney. This rising flow creates a low pressure that pulls combustion air into the chimney/plenum. Because the air enters the chimney tangentially to the flame or vertical axis, the air will tend to twist the flame.
Although this approach is an improvement over artificial or mechanically created draft devices, it nevertheless presents some difficulties. The use of vertical air slots in the sides of a chimney requires the creation of a moment with respect to a vertical axis. This approach would likely be less effective in chimneys having shapes without edges, such as tubular (i.e., cylindrical) chimneys. Such slots would likely not have a geometric configuration favorable to generating swirling effects because the tangential orientation that creates a twisting moment would be difficult to structure or would be obtrusive/aesthetically unpleasing. Moreover, because the air enters along the combined chimney/plenum or chamber, the burner must be positioned at or near the same level as the slots in order to sustain full combustion at the burner. In other words, a chimney with vertical air slots must have a cross section that accommodates the plenum and burner so that replenishment air can reach the burner, thus limiting the design options available for such chimney. Thus, the burner structure is visible, which may not be desired for an aesthetic device and may require additional screening. Notably, the air slots within the chimney are openings that expose the flame. With an open flame, the level of safety of the apparatus may render it dangerous for use about children or the inattentive. Further, the air flowing into the chimney tends to compress the flame, which necessitates a form of burner gas diverter that redirects the fuel outwardly in order to add volume to the flame. When the swirl rotates away from a portion of the diverter, the flame at the portion will break down small flamelets until the flame rotates back. It is also expected that the entry of combustion air along the course of the chimney is self limiting in that the access for combustion air is at the same point as the combustion, so that it is believed that for a given level of combustion, less of a draft would be created.
Additionally, in some embodiments, gas flow is temporarily deflected in a radial direction by the use of a series of plates. See, e.g., WO 2008/112379 A1. In such embodiments, the upward movement for much of the gas is often completely halted as it impacts the lower plate and moves outward along it. Only after reaching the edge of the plate does the gas resume its upward movement, caused by its natural buoyancy. Hence, in such embodiments, some of the kinetic energy of the gas may not be fully utilized.